The present invention relates to methods for monitoring a fluid in or near real-time and, more specifically, to methods for monitoring a fluid having one or more adulterants therein.
In the oil and gas industry, it can be important to precisely know the characteristics and chemical composition of fluids circulating into and out of subterranean hydrocarbon-bearing formations. Typically, the analysis of fluids related to the oil and gas industry has been conducted off-line using laboratory analyses, such as spectroscopic and/or wet chemical methods, which analyze an extracted sample of the fluid. Depending on the analysis required, however, such an approach can take hours to days to complete, and even in the best case scenario, a job will often be completed prior to the analysis being obtained. Furthermore, off-line laboratory analyses can sometimes be difficult to perform, require extensive sample preparation and present hazards to personnel performing the analyses.
Although off-line, retrospective analyses can be satisfactory in certain cases, but they nonetheless do not allow real-time or near real-time analysis capabilities. As a result, proactive control of a subterranean operation or fluid flow cannot take place, at least without significant process disruption occurring while awaiting the results of the analysis. Off-line, retrospective analyses can also be unsatisfactory for determining true characteristics of a fluid since the characteristics of the extracted sample of the fluid oftentimes changes during the lag time between collection and analysis, thereby making the properties of the sample non-indicative of the true chemical composition or characteristic. For example, factors that can alter the characteristics of a fluid during the lag time between collection and analysis can include, for example, scaling, reaction of various components in the fluid with one another, reaction of various components in the fluid with components of the surrounding environment, simple chemical degradation, and bacterial growth.
Monitoring fluids in or near real-time can be of considerable interest in order to monitor how the fluids change over time, thereby serving as a quality control measure for processes in which fluids are used. Specifically, adulterants present in the fluid can lead to harmful scale formation, impurity buildup, and bacterial growth which can impede processes in which the fluid is used, and even damage process equipment in certain cases. For example, water streams used in cooling towers and similar processes can become highly corrosive over time and become susceptible to scale formation and bacterial growth. Corrosion and scale formation can damage pipelines through which the water is flowing and potentially lead to system breakdowns. Similar issues can be encountered for fluids subjected to other types of environments.
Spectroscopic techniques for measuring various characteristics of fluids are well known and are routinely used under laboratory conditions. In some cases, these spectroscopic techniques can be carried out without using an involved sample preparation. It is more common, however, to carry out various sample preparation procedures before conducting the analysis. Thus, there is usually a delay in obtaining an analysis due to sample preparation time, even discounting the transit time of transporting the extracted sample to a laboratory. Although spectroscopic techniques can, at least in principle, be conducted at a job site, such as a well site, or in a process, the foregoing concerns regarding sample preparation times may still apply. Furthermore, the transitioning of spectroscopic instruments from a laboratory into a field or process environment can be expensive and complex. Reasons for these issues can include, for example, the need to overcome inconsistent temperature, humidity, and vibration encountered during field use. Furthermore, sample preparation, when required, can be difficult under field analysis conditions. The difficulty of performing sample preparation in the field can be especially problematic in the presence of interfering materials, which can further complicate conventional spectroscopic analyses.